Fix for r.js optimization build problems.

I am working on a project where I am building in postal.js 0.10.0, and was having difficulty getting the r.js optimizer to properly name/rewrite the an anonymous module so it could load correctly.

After much frustration and digging in the debugger I found out that the issue was simply conduitjs not having the empty dependency list in its UMD declaration (apparently the r.js optimizer needs this to properly process the AST?). Anyways...after adding it everything works as expected and r.js correctly renames the conduitjs anonymous module to 'conduitjs'.

So even though this is a tiny little commit, I figured you might want it...or atleast to know about the issue. I found it quite annoying ("why the hell is this thing not compiling right??!?!") ;).